Quantitative cellular assays (in vivo and in vitro) will be used to examine the interaction of radiation with selected chemotherapeutic agents as well as combination chemotherapy. AKR and L1210 leukemias, EMT6 carcinosarcoma, normal hematopoietic stem cells and L-cells in vitro are the cell lines of interest to us. We will study dose, sequence and interval to determine whether their modification can optimize cytotoxicity. A number of specific combinations of present clinical interest will also be examined for protocol input. Finally, limited biochemical studies will be carried out to help us better understand a number of the interaction which we observe.